U.S. Special Forces troops searched caves in the mountains of eastern Afghanistan Saturday for Osama bin Laden and his followers, amid reports the al-Qaida leader's voice was heard giving orders over short-range radio.
American officials could not confirm a report in the Washington Times newspaper that the al-Qaida leader's distinctive voice had been heard in intercepted radio communications.
The report said the electronic monitoring is being carried out by special operations troops on the ground, and by spy planes and satellites.
U.S. military officials have said for several days they believe Osama bin Laden is among the al-Qaeda fighters in the Agam and Wazir valleys near the border with Pakistan.
The United States has offered a $25 million reward for the al-Qaida leader, who they accuse of masterminding September 11 suicide attacks on the United States that killed more than three thousand people.
U.S. and British commandos are advancing alongside Afghan fighters in the mountainous region of eastern Afghanistan near Tora Bora. There has been fierce combat with hundreds of al-Qaida fighters trapped in the area.
Pakistan said Saturday it arrested 37 Arabs trying to sneak across the border from Tora Bora. Officials said the men admitted belonging to al-Qaida and said U.S. bombing had forced them to flee.
They were taken to a jail in southwestern Pakistan.
Fifty suspected al-Qaida members were arrested on the Pakistani side of the border earlier in the week.
In southern Afghanistan, U.S. marines are preparing a prison camp at Kandahar's airport to hold up to 300 al-Qaida fighters who might surrender or be captured in Tora Bora.